Driven by energy structure transformation, conventional thermal power pressure reducing valves with a 30%–100% load range can hardly satisfy peak-shaving demands. Meanwhile, nuclear power plant is gradually participating in deep power grid peak-shaving, making wide-load retrofitting of secondary-circuit bypass valves urgently necessary. Numerical investigations are conducted on the flow field and aerodynamic noise characteristics of a multi-stage adjustable throttling bypass valve over a valve-opening range of 5%–100%, which corresponds to a flow-load range of approximately 2.34%–107.19% of the rated flow. Results show that the three-stage structure achieves stable pressure reduction at high loads, with the third-stage orifice plate bearing over 27.55% of the total pressure drop. At low loads, the first-stage sleeve undertakes more than 91% of the pressure drop, while the pressure drop through the third-stage orifice plate is redistributed toward the first two stages. The high turbulent kinetic energy region concentrates in the second-stage pressure reduction zone, and the high Mach number region migrates from the orifice plate to the first-stage hole as load decreases. Dipole and quadrupole sound sources are consistent with flow field disturbance zones. The flow field and aerodynamic noise characteristics of nuclear power bypass valves over this wide opening range are characterized, and a numerical basis supporting the wide-load adaptive design of bypass valves in nuclear peak‑shaving scenarios is provided.

nuclear power plant peak-shaving,wide-load operation,bypass valve,flow field characteristics,aerodynamic noise characteristics